Multi-polarized single element radiator



March 2, 1965 L. D. BREETZ 3,172,111

MULTI-POLARIZED SINGLE ELEMENT RADIATOR Filed Aug. 30, 1962 2Sheets-Sheet l A N D PHASE RELATIONSHIP POWER RATIO RADIO FREQUENCYENERGY OPERATING DEVICE INVENTOR LOUIS D. BREETZ BY M M W M1 ATTORNEYMarch 2, 1965 1.. D. BREETZ 72,111

MULTI-POLARIZED SINGLE ELEMENT RADIATOR Filed Aug. 30, 1962 2 Sheets-Sheet 2 INVENTOR. LOUIS D. BREETZ ATTORNEY United States Patent Ofiice 3,172,111 Patented Mar. 2, 1965 3,172,111 MULTI-POLARIZED SINGLEELEMENT RADIATOR Louis D. Breetz, ()xon Hill, Md, assignor to the UnitedStates of America as represented by the Secretary of the Navy Filed Aug.30, 1962, Ser. No. 220,966 13 Claims. (Cl. 343730) (Granted under Title35, US. Code (1952), see. 266) The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

This invention relates to antenna systems in general and in particularto antenna systems having polarization variation properties.

In the early usage of radar systems for the detection of ships andaircraft, the predominantly horizontal extent of such large targets andthe generally more convenient horizontal orientation of linear antennaelements such as dipoles and yagi antennas provided natural complementsto each other. The advent of long, small diameter missiles and thedesire to detect them at great distances during the initial propulsionphase as Well as in a possibly tumbling or otherwise changing aspectwhile in orbit has brought about a condition in which attention must begiven to polarization optimization. Polarization diversity in itself isnothing new. Spiral antenna elements as well as crossed dipoles are wellknown and can be used in various ways to achieve polarization variation.A real difficulty arises however in connection with the detection ofobjects in orbit, where to achieve the required sensitivity anddirectivity it is not uncommon to stretch an array of dipole antennaelements in a line for several thousand feet along the earths surface.Such large arrays provide impedance matching problems particularly wherethe relatively low impedance dipoles are used and also are ofcharacteristically narrow bandwidth. Thus it is not unusual to find thatfolded dipoles have advantages particularly when it is possible to placethe dipoles at right angles to the longitudinal axis of the string ofdipoles constituting the array. This arrangement is not too well adaptedto convenient use with crossed dipole structures and hence is not suitedto polarization diversity applications.

Accordingly it is an object of the present invention to provide an arrayof folded dipoles suited for polarization diversity operation.

Another object of the present invention is to provide a folded dipoleantenna system having polarization diversity capabilities.

Another object of the present invention is to provide a folded dipolehaving all active components in a single plane and capable of producinglinearly polarized fields in orthogonally related planes as well ascircularly polarized fields of either sense and various intermediateelliptical polarization fields.

Another object of the present invention is to provide a polarizationvariable antenna in which the individual elements are of suchconfiguration as to resist relative deflections which would alter therelationship of the various polarizations.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 shows an embodiment of a single antenna ele ment and feed systemtherefor constructed in accordance with the teachings of the presentinvention.

FIG. 2 shows an array of elements of FIG. 1.

In accordance with the teachings of the present invention, apolarization diversity antenna system is pr vided which is particularlysuited for arrays having a large number of elements. The system employselements each described as a duplex folded dipole the elements being coupled to a radio frequency operative device through power ratio and phasecontrolling apparatus whereby the desired polarization is obtained inthe coupling of the elements to space.

The duplex folded dipole provides very flexible operation in that it iscapable of producing One or the other of orthogonally related linearpolarization plane couplings or of producing circular polarizationcoupling of either sense or again, when proper feed conditions exist, ofproviding intermediate elliptical polarization coupling. A duplex foldeddipole as that term is used here contains a plurality of parallelconductors disposed in close proximity, the conductors beingapproximately a half wave length in overall extent or some multiplethereof. The conductors are typically disposed in one plane with thecenter conductor being interrupted for a portion of its length atapproximately the center thereof, all conductors being connectedtogether at their outer ends. The duplex folded dipole is fed in twoWays, first at the inner-ends of the center discontinuous conductor andsecondly at the centers of the other conductors. The two feeds thusdescribed can be either simultaneous or alternating according to somedesired sequence. The result for either single feed is the production oflinearly polarized radiation, the polarization being in orthogonallyrelated planes for the two different feeds individually. If the feedsare simultaneous, of the same effective power, and possess quadraturephase relationship, the radiation from the antenna element is circularlypolarized. Where the effective powers are different and the effectivephasing is other than 0, 270 and 360, the polarization is ellipticalwith the axial-ratio and orientation of the major axes depending uponthe power ratio of the two feeds and the phasing. The sense of circularpolarization depends upon the relationship of the quadrature phasing ofthe two feeds being for example of one sense when one quadrature relatedfeed is leading with respect to the other and of the opposite sense whenthe relationship is lagging. Almost an infinite variety of linearpolarization planes is possible when the effective radiation for the twofeeds is in phase or 180 phasing merely by varying the effective powerratio for the two feeds.

Care has been exercised to speak in terms of effective power because ofthe fact that the impedances of the two antenna feeds is quitedifferent. Normally the center conductor feed is several hundred ohmswhile the feed to the outer conductors is between 500-1000 ohms.

It must also be appreciated that speaking in terms of feed power whileapparently limiting to transmit operation is merely for convenience ofexpression since the basic principle is equally applicable to thereceive operation.

With reference now to FIG. 1 of the drawings, the apparatus showntherein as previously mentioned contains a typical embodiment of anantenna element and system constructed in accordance with the teachingsof the present invention. The typical antenna element defined as aduplex folded dipole is made up of basic components 10 and 11 which aredisposed substantially in axial alignment and with a small separation oftheir adjacent ends 12 and 13 to provide an overall dipole ofapproximately a halfwave length or some multiple thereof if desired orconvenient as the discontinuous conductor mentioned in the precedingdiscussion. Such a basic antenna structure as thus far described is ofcourse readily recognized as including a conventional center fedhalf-wave dipole.

To this half-wave dipole of components 10 and 11 are added thecoextensive cooperative components 14 and 15 which are disposed in acommon plane with components 10 and 11 and substantially parallelthereto. Components 14- and 15 are continuous and of uniform dimensionsthroughout their half-wave extent. The outer ends of components 1%), 11,14 and 15 are connected together by means of conductive members 16 and17. The resulting planar structure is a device in which all portionsthereof are subjected to the same external forces which would tend toproduce deflection so that relative distortion of the elements is notparticularly troublesome as would be the case with crossed dipolesmentioned in the introduction to the specification in which, forexample, wind pressures on one dipole of crossed dipoles can beconsiderably different from the wind pressure on the other.

Two feed connections for the duplex folded dipole of FIG. 1 areprovided. The first feed is a conventional form of feed for foldeddipoles having only a single side member 14 or 15 which is at the ends12 and 13 of the center components 19-11. This basic feed is ofapproximately the 300 ohm impedance of typical folded dipoles.

A second feed for the duplex folded dipole is provided at substantiallythe centers of the components 14 and 15 which are fed in push-pullrelation to each other. The feed at the centers of components 14 and 15has substantially higher impedance than that at the points 12 and 13. Bymaking the components 10 and 11 of considerably larger diameter than thecomponents 14 and 15 reduction of the impedance at points 12 and 13 iseffected. Similarly changing the spacing of the components 14 and 15from the components 14} and 11 provides some control of the impedance atthe centers of components 14 and 15.

With the basic feed to the points 12 and 13 being linearly polarized,radiation or coupling results in which the plane of polarization issubstantially parallel to the plane of the components 110-11, 14 and 15.On the other hand with feed at the center of components 14 and 15,linear polarization also results, however, it has a plane ofpolarization which is orthogonally related to that of the first case.When the two feeds bear a quadrature phase relationship a peculiarsituation results in that the two radiations combine to effectivelyproduce circular polarization. Where the feed relationship is other thanquadrature, various polarization combinations result.

The two feeds are connected to a radio frequency energy operative device18, such as a transmitter or receiver or combination through a controldevice 19 which may typically contain a variable power splitter andvariable phase control devices whereby the power ratio and phaserelationship may be adjusted.

The field intensity pattern for the antenna of FIG. 1 is in generalsimilar to that of a folded dipole for both polarization planes beingmaximum normal to the longitudinal axis of the element. An E-plane fieldPattern for both modes of approximately 90 degree beamwidth between thethree db levels and an H-plane pattern of approximately 160 degreesbetween the three db levels was obtained in a typical experimentalinstallation for this duplex dipole placed over a ground plane.

As in a normal folded dipole, or any dipole for that matter, the fieldpattern can be adjusted appreciably by changing the spacing between theelement and the ground plane. In this respect this element is similar toother dipole elements.

In a typical embodiment of the apparatus of FIG. 1 intended for halfwave operation at a frequency of 108 megacycles per second, the overalllength of the components including members 16 and 17 was typically 54inches with a center to center spacing of the components 14 and 15 being5 inches, components and 11 being disposed midway between 14 and 15. Thespacing of the feed points 12 and 13 was typically 1 inch While thecomponents 14) and 11 were constructed of material having 1% inchdiameter, the diameter of components 15 and 14 and the members 16 and 17being approximately of an inch. It was determined that the impedance atpoints 12 and 13 under such conditions as outlined under the foregoingwas approximately 280 ohms whereas the impedance fed at the centers ofcomponents 14 and 15 was approximately 700 ohms.

FIGS. 2 indicates a typical arrangement wherein a plurality of duplexfolded dipole antennas of the type of FIG. 1 can be effectively placedin an array for purposes of achieving improved sensitivity anddirectivity. The particular array is such as would find utility in anupward looking system for the detection of the passage overhead of earthsatellites. A refilector 50 of wire mesh is mounted substantiallyhorizontally above the surface of the earth.

Above the reflector 50 a plurality of duplex folded dipoles 51 areplaced. These dipoles are individually disposed normal to thelongitudinal axis of the array with the plane of the components (10-11,14, 15 of FIG. 1) also perpendicular to the axis of the array. Theelements are spaced a half wavelength apart along the longitudinal axisand suitably supported as from the reflector support structure bymembers 52.

The members 52 also provide as by a hollow construction, a shieldedpassage for the feed lines and, with suitable insulation, fixed relativepositioning of the elements in the central region.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An antenna element comprising, first and second rod-type componentsdisposed one end of one to one end of the other with their longitudinalaxis in substantial coincidence, the adjacent ends being insulated fromeach other, the overall extent along the longitudinal axis to the outerends being substantially a multiple including unity of a halfwavelength.

third and fourth rod-type components substantially a multiple includingunity of half wavelengths long disposed adjacent and parallel to thecombination of the first and second components, in substantially thesame plane and with the ends in substantially the same planes as theouter ends of the first and second components,

means connecting the outer ends of the first and second components tothe adjacent ends of the third and fourth components,

first energization means for enabling energization of said first andsecond rod-type components as a halfwave dipole antenna,

and second energization means for enabling energization of each of saidthird and fourth rod-type components at a point substantiallyintermediate their respective outer ends.

2. An antenna element comprising, first and second rod-type componentsdisposed one end of one to one end of the other with their longitudinalaxes in substantial coincidence, the adjacent ends being insulated fromeach other, the overall extent along the longitudinal axis to the outerends being substantially a multiple including unity of a half-wavelength,

third and fourth rod-type components substantially a multiple includingunity of a half wavelength long disposed adjacent and parallel to thecombination of the first and second components, in substantially thesame plane and with the ends in substantially the same planes as theouter ends of the first and second components,

means connecting the outer ends of the first and second components tothe adjacent ends of the third and fourth components,

first transmission line means for connecting to the first and secondcomponents at the adjacent ends thereof, second transmission line meansfor connecting to the 23 third and fourth components at the centersthereof,

a radio frequency operative device,

and means for coupling the said device to said transmission lines inselected relative phase and power ratio.

3. An antenna according to claim 1 wherein said second energizationmeans enables energization of said third and fourth rod-type componentsin push-pull relation to each other.

4. An antenna according to claim 3 wherein said first and secondenergization means include means for selectivity energizing said firstand second rod-type components as a unit and said third and fourthrod-type components as a unit either individually or simultaneously.

5. An antenna according to claim 1 wherein said first and secondrod-type components are of identical uniform cross-section, and whereinsaid third and fourth rod-type components are of identical uniformcross-section but of a cross-section smaller than said first and secondrodtype components.

6. An antenna according to claim 1 wherein said first and secondenergization means include means to enable energization of said first,second, third and fourth rodtype components in selected relative phaseand power ratio.

7. The combination comprising a plurality of antenna elements as definedin claim 1 arranged in linear array with their planes disposed inparallel relationship to each other and spaced substantially a half-wavelength apart, and a planar radiant energy reflector for said lineararray lying in a plane substantially perpendicular to the parallelplanes of said plurality of antenna elements.

8. The combination of claim 7 wherein said reflector is a wire mesh.

9. A transmit-receive duplex antenna comprising in combination,

a first antenna unit defined by a pair of conductive elements forming acenter-fed half-wave dipole,

a second antenna unit defined by a pair of linear conductors, each ofsaid conductors being coextensive with the length of said dipole andpositioned on opposite sides of said dipole elements in parallel andplanar relationship therewith, said conductors having energy feedconnections at a point substantially intermediate their respective outerends,

means connecting the outer ends of said dipole elements to the outeradjacent ends of said pair of conductors,

and radio frequency operating means operatively associated with saidfirst and second antenna units to selectively enable said antenna unitsto operate individually or simultaneously.

10. A duplex antenna according to claim 9 wherein said conductors are ofuniform cross-section but smaller than the cross-section of said dipoleelements.

11. A duplex antenna according to claim 9 wherein said radio frequencyoperating means include adjustable means to enable said first and secondantenna units to operate in selected phase and power ratio relationship.

12. The combination comprising a plurality of duplex antennae as definedin claim 11 arranged in a linear array with their planes disposed inparallel relationship to each other and spaced substantially a half-wavelength apart,

and a planar radiant energy reflector for said linear array lying in aplane substantially perpendicular to the parallel planes of saidplurality of duplex antennae.

l3. duplex antenna comprising,

a three conductor folded dipole having the center conductor interruptedsubstantially at the center thereof to enable said center conductor tooperate as a center-fed half-wave dipole,

connection means at the center of each of the outer conductors of saidfolded dipole to enable said outer conductors to operate as an antennaunit,

and means for selectively enabling said operationally formed center-fedhalf-wave dipole and said operationally formed antenna unit to operateindividually or simultaneously.

References Cited by the Examiner UNITED STATES PATENTS 2,234,744 3/41Thomas 343-804 X 2,345,735 4/44 Douma 343-804 X 2,703,840 3/55Carmichael 343-804 2,825,061 2/58 Rowland 343-743 X 2,953,781 9/60Donnellan et al. "343-858 HERMAN KARL SAALBACH, Primary Examiner.

1. AN ANTENNA ELEMENT COMPRISING, FIRST AND SECOND ROD-TYPE COMPONENTSDISPOSED ONE END OF ONE TO ONE END OF THE OTHER WITH THEIR LONGITUDINALAXIS IN SUBSTANTIAL COINCIDENCE, THE ADJACENT ENDS BEING INSULATED FROMEACH OTHER, THE OVERALL EXTENT ALONG THE LONGITUDINAL AXIS TO THE OUTERENDS BEING SUBSTANTIALLY A MULTIPLE INCLUDING UNITY OF A HALFWAVELENGTH, THIRD AND FOURTH ROD-TYPE COMPONENTS SUBSTANTIALLY MULTIPLEINCLUDING UNITY OF HALF WAVELENGTHS LONG DISPOSED ADJACENT AND PARALLELTO THE COMBINATION OF THE FIRST AND SECOND COMPONENTS, IN SUBSTANTIALLYTHE SAME PLANE AND WITH THE ENDS IN SUBSTANTIALLY THE SAME PLANES AS THEOUTER ENDS OF THE FIRST AND SECOND COMPONENTS, MEANS CONNECTING THEOUTER ENDS OF THE FIRST AND SECOND CONPONENTS TO THE ADJACENT ENDS OFTHE THIRD AND FOURTH COMPONENTS, FIRST ENERGIZATION MEANS FOR ENABLINGENERGIZATION OF SAID FIRST AND SECOND ROD-TYPE COMPONENTS AS A HALFWAVEDIPOLE ANTENNA, AND SECOND ENERGIZATION MEANS FOR ENABLING ENERGIZATIONOF EACH OF SAID THIRD AND FOURTH ROD-TYPE COMPONENTS AT A POINTSUBSTANTIALLY INTERMEDIATE THEIR RESPECTIVE OUTER END.